Embodiments of the present invention relate to a rechargeable battery and methods of manufacturing the same.
A rechargeable thin film battery typically comprises a substrate having thin films that cooperate to store and release electrical charge. Thin-film batteries typically have a thickness that is less than about 1/100th of the thickness of conventional batteries, for example, a thickness of less than about 0.5 mm. The thin films may be formed on the substrate by conventional fabrication processes, such as for example, physical or chemical vapor deposition (PVD or CVD), oxidation, nitridation, electron beam evaporation, and electroplating processes. The thin films typically include cathode, electrolyte, anode, and current collector films. When the rechargeable battery is charged, ions formed of the cathode material pass from the cathode through the electrolyte to the anode, and when the battery is discharged these ions travel back from the anode through the electrolyte to the cathode. For example, in batteries having a cathode comprising lithium, such as a LiCoO2 or LiMnO2 cathode, lithium species originating from the lithium-containing cathode travel from the cathode to the anode and vice versa during the charging and discharging cycles, respectively.
Several types of anodes are commonly used for lithium cathode batteries. The first anode type is made from a material that accepts lithium ions, such as tin oxide. The lithium ions travel into and out of the anode during charging and discharging of the battery. However, such anode materials can often consume, irreversibly, between 40 to 60% of the lithium of the cathode. It is undesirable to consume such large amounts of the lithium during charging and discharging of the battery as this limits the energy storage capacity of the battery.
Another type of anode comprises a lithium layer upon which, during charging, lithium material from the cathode deposits upon and gradually builds up. The original lithium anode provides nucleation sites for the cathode generated lithium material and accommodates the stresses that result from the deposition and removal of the lithium material. However, the lithium layer typically deteriorates when exposed to air, which complicates fabrication of the battery. Also, the battery cannot always be assembled using common metal joining processes, such as solder re-flow, because of the low melting temperature of lithium (181xc2x0 C.).
Yet another type of battery, commonly known as the lithium-anode-free battery is fabricated with only a layer of metal as a current collector and without a preformed lithium anode. Instead, a lithium anodic film is formed at the interface of the current collector and the electrolyte of the battery during the first charge-up cycle of the battery. Thereafter, during subsequent charge and discharge cycles, the battery operates with the lithium anodic film that is generated from the initial charge-up cycle. However, the in-situ generated lithium anodic film is often non-uniform in thickness resulting in the generation of stresses in the battery. The formation and dissociation of lithium at the cathode current collector/electrolyte interface during the charging and discharging cycles can cause the anode current collector to separate from the electrolyte. Also, the non-uniform thickness of in-situ formed lithium anode and the separation of the cathode current collector from the electrolyte lead to a gradual decrease in the energy storage capacity and an increase in the leakage current over multiple charging and discharging cycles.
The long-term performance of the Li-free battery over multiple cycles may be improved by forming an overlayer of parylene or LiPON over the anode current collector. The overlayer has been found to reduce the gradual loss of energy storage capacity over multiple battery cycles, as for example, described by Neudecker et. al. in U.S. Pat. No. 6,168,884 and in the Journal of the Electrochemical Society, 147 (2), 517-523 (2000), both of which are incorporated herein by reference in their entireties. Such a battery consists of a cathode, an electrolyte film, an anode current collector and the overlying layer of parylene or LiPON on the anode current collector. During each charge and discharge cycle in which the lithium anode film is formed and then gradually dissipated, the anode current collector along with the overlying layer is lifted up from, or set down onto, the electrolyte layer. This process becomes reversible only when an overlying film is deposited onto the anode current collector, and without the overlying layer, the battery suffers a loss of capacity with increasing cycles. However, even such types of batteries develop stresses arising from the non-uniform thickness of the lithium anode that often results in a path for current leakage. Also, the deposition of the overlying layer increases the cost of the battery and the extra layer reduces the energy density factor of the batteryxe2x80x94which is the energy stored per unit volume of the battery.
Thus it is desirable to provide a rechargeable battery that maintains good energy storage capacity after numerous charge and discharge cycles. It is further desirable for the rechargeable battery to maintain its structural integrity after a number of charging and discharging cycles. It is also desirable to have a lithium-anode-free battery that can maintain its properties over numerous cycles, without losing its structural integrity, and while still having a good energy density factor.
A rechargeable battery has a battery cell at least partially enclosed by a casing. The battery cell comprises (1) a substrate; (2) a cathode and cathode current collector on the substrate, the cathode being electrically coupled to the cathode current collector; (3) an electrolyte electrically coupled to the cathode or cathode current collector; and (4) a permeable anode current collector having a first surface electrically coupled to the electrolyte and an opposing second surface, the permeable anode current collector: (1) having a thickness that is less than about 1000 xc3x85 and that is sufficiently small to allow cathode material to permeate therethrough to form an anode on the opposing second surface of the permeable anode current collector when the battery cell is electrically charged, and (2) that is absent an overlayer on the opposing second surface of the anode current collector. Positive and negative terminals are electrically connected to the battery cell.
A rechargeable battery comprises (a) a casing; (b) a battery cell at least partially enclosed by the casing, the battery cell comprising: (1) a substrate, (2) a cathode and cathode current collector on the substrate, the cathode being electrically coupled to the cathode current collector, (3) an electrolyte electrically coupled to the cathode or the cathode current collector, and (4) a permeable anode current collector having a first surface electrically coupled to the electrolyte and an opposing second surface, the permeable anode current collector comprising a grid having perforations that allow cathode material to pass through the perforations to form an anode on the second surface or in the perforations when the battery cell is electrically charged; and (c) positive and negative terminals that electrically connect to the battery cell.
A method of forming a rechargeable battery comprises:
(a) forming a battery cell by the steps of:
(1) forming a substrate,
(2) forming a cathode and cathode current collector on the substrate, the cathode being electrically coupled to the cathode current collector,
(3) forming an electrolyte electrically coupled to the cathode or the cathode current collector, and
(4) forming a permeable anode current collector having a first surface electrically coupled to the electrolyte and an opposing second surface, the permeable anode current collector having (1) a thickness that is less than about 1000 xc3x85 and that is sufficiently small to allow cathode material to permeate therethrough to form an anode on the second surface of the permeable anode current collector when the battery cell is electrically charged, and (2) absent an overlayer on the second opposing surface;
(b) connecting positive and negative terminals to the battery cell; and
(c) enclosing the battery cell at least partially within a casing.
A method of forming a rechargeable battery comprises:
(a) forming a battery cell by the steps of:
(1) forming a substrate,
(2) forming a cathode and cathode current collector on the substrate, the cathode being electrically coupled to the cathode current collector,
(3) forming an electrolyte electrically coupled to the cathode or the cathode current collector, and
(4) forming a permeable anode current collector having a first surface electrically coupled to the electrolyte and a second opposing surface, the permeable anode current collector comprising a grid having perforations that allow cathode material to pass through the perforations to form an anode on the second surface of the anode current collector or in the perforations when the battery cell is electrically charged;
(b) connecting positive and negative terminals to the battery cell; and
(c) enclosing the battery cell at least partially within a casing.